Bug #21256: `it` value is wrapped in an array when that doesn't happen with numbered parameter

• Status: Closed
• Assignee: prism
• Target version: -
• ruby -v: ruby 3.4.2 (2025-02-15 revision d2930f8e7a) +PRISM [x86_64-linux]
• Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN

[Earlopain (Earlopain _)]

I have the following script:

require "bundler/inline"

gemfile do
  source "https://rubygems.org"

  gem "rspec-core", "3.13.3"
  gem "rspec-expectations", "3.13.3"
end

require "rspec/autorun"
require "rspec/expectations"

RSpec::Matchers.define :example do
  chain(:foo) { pp _1 }
  chain(:bar) { pp it }
end

RSpec.describe "demo" do
  it do
    example.foo(1)
    example.bar(2)
  end
end

It calls two methods were the only difference is that one accesses the argument with _1, the other with it. It prints the following:

1
[2]

So, it for some reason wraps it in an array. I appologise for the reproduction script, it uses rspec and the amount of metaprogramming it uses makes it impossible for me to reduce this further.

When running with parser=parse.y, the expected output is returned (just 2, no array). I also tested against current ruby-dev and it also happens there.

[mame (Yusuke Endoh)]

• Status changed from Open to Assigned
• Assignee set to prism

Here is a repro without rspec.

class C
  define_method(:foo) do
    p it
  end
end

class D < C
  def foo(*args)
    super(*args)
  end
end

D.new.foo(1)

$ ./local/bin/ruby --parser=parse.y t.rb
1

$ ./local/bin/ruby --parser=prism t.rb
[1]

[Earlopain (Earlopain _)]

Thanks for that info, it allowed me to make a potential fix: https://github.com/ruby/ruby/pull/13108

[Earlopain (Earlopain _)]

• Status changed from Assigned to Closed

Applied in changeset git|265059603c3aa6a13f90096c71b32046a17938f3.

---

[Bug #21256] Fix it parameter when splatting and define_method is used

It was failing to set the leads, like numblocks do, causing the result to be wrapped in an array

[mame (Yusuke Endoh)]

• Status changed from Closed to Open

That fix caused an ASAN error. I will revert it for now. See https://github.com/ruby/ruby/pull/13947

[mame (Yusuke Endoh)]

• Status changed from Open to Closed

Applied in changeset git|dc8ae249517e017e52a4b34a14ddd594a706a9d5.

---

Revert "[Bug #21256] Fix it parameter when splatting and define_method is…"

This reverts commit 265059603c3aa6a13f90096c71b32046a17938f3.

[mame (Yusuke Endoh)]

• Status changed from Closed to Open

[Earlopain (Earlopain _)]

Sorry about that. It looks like removing the first handling of PM_IT_PARAMETERS_NODE you wrote about in https://github.com/ruby/ruby/pull/13947 runs into https://bugs.ruby-lang.org/issues/20965 / https://github.com/ruby/ruby/commit/667a0f9f928be843a0810f2c61b633be1f8cd46a

For example the change

  1) Failure:
TestProc#test_parameters_lambda [/home/mame/work/ruby/test/ruby/test_proc.rb:1445]:
<[[:req]]> expected but was
<[[:req, :it]]>.

is consistent with how numbered parameters are handled:

proc { _1 }.parameters(lambda: true)
=> [[:req, :_1]]

But yeah, looks like it is not so trivial. I will leave the fix up to someone else more experienced.

[kddnewton (Kevin Newton)]

• Status changed from Open to Closed

Applied in changeset git|4f4b4e3b37c884093a165801b5028c14a7de1604.

---

Fill in lead num for blocks with it

Fixes [Bug #21256]

Co-Authored-By: Earlopain [e-mail]